Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 42 for “"ammonia-oxidation"”.
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A study of the conversion efficiency of an ammonia oxidation unit
Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1929.
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Low pressure ammonia oxidation over supported cobalt catalyst for nitric acid production
Ammonia oxidation is used in the production of nitric acid. The process is either run at high pressure or low pressure, with the latter requiring larger equipment. Platinum gauze is typically used as a catalyst operating at high temperatures (in the range of 810-940 ᵒC). The platinum based catalyst …
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The role of copper proteins in the ammonia oxidation pathway of Nitrosopumilus maritimus
The contribution of ammonia oxidising archaea (AOA) to the global nitrogen cycle has become apparent in recent years. Where previously thought to be driven by bacteria, archaea may outcompete bacteria, particularly in low nutrient environments like unfertilised soils. Ammonia oxidising bacteria …
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The impact of metals and other stress factors on microbial ammonia oxidation physiology and isotope effects
… quality, ecosystem health, and climate change. Ammonia (NH3) oxidation, the first and rate-limiting step of nitrification, is carried out by bacteria (AOB) and archaea (AOA). Despite more than a century of research into the physiology of AOB, and only more recently AOA, fundamental questions …
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Performance and microbial community structure of Midwestern groundwater pretreatment reactors
Biological ammonia oxidation has received considerable industry research recently as water utilities seek to minimize chlorine demand and potential disinfection byproduct formation. Many plants are forced to chlorinate before primary filtration in order to meet disinfection requirements, so a …
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Deammonification Process Kinetics and Inhibition Evaluation
… liquor, can cause an increase of up to 25% in ammonia loading. The recently discovered anaerobic ammonia oxidation (anammox) process is a major breakthrough for treatment of these streams as it has the potential to remove up to 85% of nitrogen load without external carbon source addition. The …
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Micropollutants biotransformation by two nitrifying communities enriched from biofilm of a nitrification trickling tower
… effects. It has been hypothesized that ammonia-oxidizing bacteria (AOB) were responsible for micropollutants biotransformation, which contributes to the removal of micropollutants. Both inhibition studies and pure culture studies have been performed to test this hypothesis. By inhibiting …
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Oxygen isotope systematics of nitrification
… The lab experiments tested the exchange in ammonia oxidation, using ammonia oxidizing bacteria, Nitrosomonas sp. C113a and Nitrococcus oceani, and nitrite oxidation using cultures of the nitrite oxidizing bacterium, Nitrosococcus mobilis. The exchange value in the ammonia oxidation …
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Microbial nitrogen-cycling and cooperation in the terrestrial subsurface
… denitrification, anaerobic ammonium oxidation (anammox), and assimilation. The microorganisms that perform these processes can be sources and sinks of nitrate – a major anthropogenic contaminant of aquifers. Therefore, it is crucial that we understand how natural and anthropogenic …
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Kinetic studies of ammonia-oxygen flames
<p>Since the early interest of Henry in burning ammonia with electric sparks, the literature of ammonia oxidation has been extensive. The major efforts have been industrially related and concern themselves with catalytic oxidation and its mechanism. The flame oxidation of ammonia has attracted more …
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A novel mechanism for metal alloying at the nanoscale
… prove utility, we synthesized quinary HEA-NPs as ammonia oxidation catalysts with -100% conversion and >99% nitrogen oxide selectivity over prolonged operations. This mechanism is distinct from previously reported alloying processes, which can bring about a new repertoire of alloys and …
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The biogeochemistry of marine nitrous oxide
… and the ocean. Nitrification, and particularly ammonia oxidation, is one of the major processes that produces N2O in the ocean. In this thesis, a series of stable isotopic methods have been used to characterize the biogeochemical controls on N2O production by marine nitrification as well as the …
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Nitrogen cycling in oxygen deficient zones : insights from [delta]¹⁵N and [delta]¹⁸O of nitrite and nitrate
… the dominant source and sinks of nitrite are ammonia oxidation and nitrite oxidation with an average age of 37 days. Finally, using the isotope systematics of nitrification as well as the properties of nitrite oxygen isotope exchange described in this thesis, the final chapter interprets …
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Breakpoint Chlorination as an Alternate means for Ammoia-Nitrogen removal at a Water Reclamation Plant
… are currently available for nitrogen removal or ammonia conversion to nitrate. Those that are economically feasible rely mostly on microbiological processes, which are only effective when the microorganisms remain in a healthy state. If a biological process upset was to occur, due to a toxic …
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The biogeochemistry of marine nitrous oxide
… and the ocean. Nitrification, and particularly ammonia oxidation, is one of the major processes that produces N₂O in the ocean. In this thesis, a series of stable isotopic methods have been used to characterize the biogeochemical controls on N₂O production by marine nitrification as well as the …
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Ecology and adaptation of denitrifiers across genomes and environments
… nitrogen cycle, including losses from anaerobic ammonia oxidation (anammox) and denitrification. The stepwise reduction of nitrate to nitrite, nitric oxide, nitrous oxide, and N2 gas, denitrification can be performed by diverse taxa and acts as a major sink of fixed nitrogen within low oxygen …
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The Effect of Chlorine and Chloramines on the Viability and Activity of Nitrifying Bacteria
… events, including optimizing the chlorine-to-ammonia ratio, maintaining chloramine residual throughout the distribution system, controlling pH, and temporal switching to free chlorination. Annual or semi-annual application of free chlorination is practiced by 23% of chloraminating systems on a …
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Simultaneous Nitrification and Denitrification of Wastewater Using a Silicone Membrane Aerated Bioreactor
… treat wastewater by simultaneously oxidizing ammonia, and reducing nitrate and nitrite. The Environmental Protection Agency (EPA) places strict discharge restrictions on these compounds due to their inherent toxicity to humans, wildlife, and ecosystems. The use of a simultaneous system can …
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Perennial energy crops on riparian buffers affect nitrogen cycling microbial communities
… of N cycling functional groups involved in ammonia oxidation (amoA), nitrite ammonification (nrfA), denitrification (nirK, nirS, norB, and nosZ), and N fixation (nifH). The results indicated that N application significantly affected the abundance of four different functional enzyme groups. …
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